Hi John,

The GDB you're using should be fine.  Your error is most likely a bug in
the GDB implementation in the RISC-V ISA within gem5.  I can take a look at
it over the next week or so, but if you find a fix for it yourself don't
hesitate to submit a patch.

-Alec Roelke

On Wed, Jul 17, 2019 at 3:19 PM John Liu <[email protected]> wrote:

> Hi, colleges,
>
> I'm trying to use remote gdb debug for RISCV/gem5.debug in FS mode. The
> binaries file I used to try this interface is the Berkely boot loader and
> it has been able to boot in FS mode.
>
> * I enabled the "wait_for_remote_gdb" Params in BaseCPU.py and this Params
> worked.
>   But GDB part (riscv64-unknown-elf-gdb) returned glitch.
>
> * I tried the "hello world" binary with riscv64-unknown-elf-gdb in SE
> mode.
>   The similar glitch happened.
>
> * I also tried the remote debug the Berkeley boot loader in Qemu with the
> same gdb tool. It works.
>
> Did I pick the wrong Riscv GDB tool for gem5? Did I miss anything?
>
> Any opinion will be helpful. I appreciate your time and help!
>
> Attached are the commands I used and the message I got:
> ** Commands
> *** The command I used for FS mode is :
>       build/RISCV/gem5.debug configs/example/riscv_fs.py
> *** The command  I used for remote gdb is:
>       riscv64-unknown-elf-gdb -f bbl3
>       (gdb) target remote : 7000
>
> ** Messages
> *** The message I got from Gem5:
> gem5 Simulator System.  http://gem5.org
> gem5 is copyrighted software; use the --copyright option for details.
>
> gem5 compiled Jul 17 2019 11:55:28
> gem5 started Jul 17 2019 11:59:25
> gem5 executing on riscv_fs, pid 14710
> command line: build/RISCV/gem5.debug configs/example/riscv_fs.py
>
>
> Global frequency set at 1000000000000 ticks per second
> warn: DRAM device capacity (8192 Mbytes) does not match the address range
> assigned (32768 Mbytes)
> info: kernel located at: /home/ riscv_fs/gem5/gem5_ad2039/bbl3
> 0: system.remote_gdb: listening for remote gdb on port 7000
> info: system.cpu: Waiting for a remote GDB connection on port 7000.
>       0: system.remote_gdb: remote gdb attached
> start load DTB file/home/riscv_fs/gem5/gem5_ad2039/cpu.dtb
> Beginning simulation!
> info: Entering event queue @ 0.  Starting simulation...
> warn: Couldn't read data from debugger.
>       0: system.remote_gdb: remote gdb detached
> This is bbl's dummy_payload.  To boot a real kernel, reconfigure bbl
> with the flag --with-payload=PATH, then rebuild bbl. Alternatively,
> bbl can be used in firmware-only mode by adding device-tree nodes
> for an external payload and use QEMU's -bios and -kernel options.
>
>     chosen {
>         riscv,kernel-start = <payload_start>;
>         riscv,kernel-end = <payload_end>;
>     };
> *** message I got from gdb is:
> Remote debugging using : 7000
> Remote 'g' packet reply is too long (expected 532 bytes, got 1468 bytes):
> 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003000000000000002d111400000000000000000000000000000000000000000000000000002000000a0000000000000000000000000000000000000000000000000000003f702f5d000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
>
>
>
>
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